They can also be found filled with poppyseed filling, which can be homemade or bought in cans in the baking section of the grocery store. Hammantaschen can be filled with anything really, if you aren't bent on making them traditional. I would go for something fun and seasonal like an apple/cinnamon filling (chop apples and cook them down with a sprinkle of cinnamon and sugar to taste, salt and lemon juice).

Thank you pierino! my thought also. :D Never heard of nectarine filling for Hamantaschen, altho I don't know why not, except I like my fillings to be dark. (Haman's hat was black, after all.) I fill my Hamantaschen with poppy seed, prune, blueberry or chopped chocolate to achieve that effect. They all taste great.